Update README.md

src/vloam_main/README.md

@@ -5,7 +5,8 @@ PCL 1.2
 
 # Usage 1
 
-- Step 1, download bag files under "/bags"
+- Step 1, create and move bag files to "REPO_ROOT/src/vloam_main/bags"
+  - For example: https://github.com/tomas789/kitti2bag
 
 - Step 2, `catkin_make`, and then `roslaunch vloam_main vloam_main.launch` (Toggle param ```save_traj``` to save odometry path into txt)
 
@@ -118,4 +119,4 @@ Except from static transformations, VLOAM has three odometry sources: VO, LO, MO
 - Section 4: Solve VO // takes ~11ms
 - Section 5: Publish VO
   - `dynamic_broadcaster.sendTransform(world_stamped_tf_base);` is the final result from VO. Base_link of the vehicle on the ground serves at the bridge between other frames on vehicle and world coordinate `map`. `world` frame is occupied by rosbag, so `map` is the world here.
-  - Before that, `velo_last_T_velo_curr` updates the VO result in velodyne frame.
+  - Before that, `velo_last_T_velo_curr` updates the VO result in velodyne frame.